1. Field of the Invention
The present invention relates to a structure of a semiconductor device incorporating, as one package, a power semiconductor chip that performs a large-current operation and a control semiconductor chip controlling the power semiconductor chip mounted together on a lead frame.
2. Description of the Related Art
A power semiconductor element (rectification diode, power MOSFET, IGBT, etc.) that performs large current switching or large current rectification generates a large amount of heat during operation. Thus, it is desirable for a power semiconductor module incorporating such a power semiconductor element in a mold material to have a high heat dissipation efficiency.
Such a configured power semiconductor module is disclosed in, e.g., Patent Document 1 (Japanese Patent No. 3,250,213). In such a power semiconductor module, a lead frame constituted by a radiator plate and lead terminals (leads) is used, and a power semiconductor chip is mounted on the radiator plate. This structure is sealed by a resin mold material, and the solidified mold material forms a package. The lead frame is made of copper, etc., having a high thermal conductivity. The lead terminals constituting a part of the lead frame are protruded from the mold material. Electrodes of the power semiconductor chip are connected to the respective leads constituting electric signal input/output terminals using bonding wires, etc. The power semiconductor chip operates with a voltage externally applied to each lead. In actual use of the power semiconductor module having such a configuration, the leads are inserted into through-holes formed in a printed circuit board and soldered to the printed circuit board. Alternatively, a configuration may be adopted in which not only the leads are protruded from the mold material but also the radiator plate is exposed on the rear side of the mold material. In this case, the rear-side radiator plate itself may be soldered to the printed circuit board.
The thermal conductivity of the mold material is not higher as compared to that of the lead frame. Thus, how heat generated from the power semiconductor chip is released outside through the lead frame is important in order to increase the heat dissipation efficiency. That is, heat generated from the power semiconductor chip is directly released outside through the leads led out from the mold material or through the radiator plate, or indirectly released outside through the mold material.
However, there may a case where the power semiconductor chip and a control IC chip are mixedly mounted in the power semiconductor module. In this case, heat generated from the power semiconductor chip is transferred to the control IC chip, and the temperature of the control IC is increased, which may result in performance degradation. That is, a temperature rise of the power semiconductor chip is transferred to the control IC chip, etc., which may prevent proper operation of the power semiconductor module. In Patent Document 1, the control IC chip and power semiconductor chip are mounted on a single lead frame, which is disadvantageous in terms of heat dissipation. That is, in the conventional technique as described above, heat generated from the power semiconductor chip cannot be released outside in a satisfactory manner but the temperature rise of the control IC chip, etc., occurs, making it difficult to obtain a high-reliable power semiconductor module. Further, since a terminal for outputting a high voltage from the power semiconductor chip and a terminal for outputting a low voltage from the control IC chip are arranged in parallel, a problem remains in terms of voltage resistance.
This results in difficulty in obtaining a high-reliable semiconductor device having an improved heat dissipation property.